The lost-pattern (or lost wax) casting method is a well-known casting method that is used in particular for fabricating turbine blades, in particular for aeroengines, in particular gas turbine engines. By way of example, the method is described in Document WO 2014/049223.
When performing that casting method to fabricate a cluster of castings, a cluster of castings is obtained that is formed in an “investment” or shell. This shell is typically made of ceramic. It is referred to herein either as a “shell” or as a “shell mold”.
In order to finalize fabrication of castings, it is therefore necessary to extract them: this operation is known as “knocking out”.
Traditionally, knocking out is performed by knocking against the shell with a hammer so as to break it and detach it from the cluster of castings.
That technique nevertheless suffers from two drawbacks: firstly, it is tedious and tiring for the operators performing those operations; and secondly it can lead to mechanical stresses in the castings. During subsequent heat treatment, such mechanical stresses can give rise to the appearance of metallurgical defects known as “recrystallized grains”. Such grains of recrystallized metal are zones of weakness that reduce the lifetime of the parts that are obtained and that can lead to them being rejected.